Field of the Invention
The present invention relates to a signal processing technology of resizing an image signal.
Description of the Background Art
As to a technique of resizing input signals such as an image signal, for example, in Japanese Patent Application Laid-Open No. 1-293007 discloses a sampling filter that reduces a frequency F of the input signal to a frequency F/M (M is an integer).
In downscaling an input image signal input in synchronization with a timing signal to the image signal synchronized with a sampling signal having a slower period by the technique, a scale factor of a signal interval of the timing signal and a signal interval of the sampling signal is previously acquired, and it is necessary to set a resizing ratio for resizing processing of generating (reconstructing) an output image signal using an average value of the plural input image signals.
In the technique, in the case that the output image signal is generated in synchronization with the sampling signal having an unknown period, because a parameter used in resizing processing performed by an image signal generating circuit (resizing circuit) is not fixed, there is a problem in that the average value of the input image signals cannot be obtained with the proper scale factor.
In the case that an interval of the timing signal or sampling signal is unequal, because previously-set scale factors for the periods of the timing signal and sampling signal differ from the actual scale factors, there is a problem in that the resizing is hardly performed by accurately obtaining the average value.
Specifically, for example, in a printing system that performs printing while inspecting a printed image, in the case that the image signal sequentially output from a camera provided with a line sensor, which extends in parallel with a paper surface so as to be orthogonal to a main scanning direction, at constant time intervals is resized in synchronization with an encoder signal corresponding to a paper conveying speed, the paper conveying speed varies due to expansion and contraction of paper, and the period of the encoder signal varies. For this reason, a resizing ratio cannot properly be corrected, but the resizing is locally performed with the scale factor different from actual one, which results in a possibility that a false inspection result is generated.